The effect of tether substituents on the selectivity of Pd catalyzed enyne cyclizations. A total synthesis of chokol C

In the context of the palladium catalyzed cycloisomerization of enynes, two of the most important tether substituents, the carbonyl group because of its general synthetic versatility and the ketal because of its prospect to induce absolute stereochemistry by employing the ketal from a chiral diol, are probed within the context of a synthesis of chokol C, an antifungal compound produced by Phleum pratense when infected by a pathogenic fungus Epichloe typhina.